System, devices, and method for on-body data and power transmission

ABSTRACT

An on-body sensor system includes a hub configured to be attached to a surface of a user. The hub being further configured to transmit electrical power and/or data signals into the surface and to receive response data signals from the surface. The system further including at least one sensor node configured to be attached to the surface. The sensor node being further configured to receive the electrical power and data signals from the hub through the surface and to transmit the response data signals into the surface. The electrical power from the hub can power the sensor node and cause or enable the at least one sensor node to generate sensor information that is transmitted back to the hub within the response data signals.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to and the benefit of U.S.Provisional Application No. 62/298,296, filed Feb. 22, 2016, entitled,“SYSTEM, DEVICES, AND METHOD FOR ON-BODY DATA AND POWER TRANSMISSION,”which is hereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present disclosure relates to on-body, multi-sensor networks. Inparticular, the present disclosure relates to the delivery of electricalpower and data signals within an on-body, multi-sensor network.

BACKGROUND OF THE INVENTION

With advancements in the manufacturing of semiconductor devices, suchdevices are becoming smaller and more versatile. These devices arespurring advancements in different and new technological areas. Onetechnological area is wearable devices. Despite the advancements in thesemiconductor devices themselves, however, the current state of powersources still imposes limitations on the semiconductor devices. In thefield of wearable devices, the form factor and longevity of wearabledevices are directly related to the on-board power sources. The powersources for wearable devices are typically in the form of bulky(relative to the size of the wearable devices), non-conformal batteries,such as lithium ion batteries. The size of the batteries drives theoverall form factor of the wearable devices to be large, bulky, and/ornon-conformal, which imposes limitations and constraints on the overallfunctionality of the wearable devices.

Therefore, there is a continuing need for developing systems, methods,and devices that solve the above and related problems.

SUMMARY OF THE INVENTION

According to some embodiments, an on-body sensor system includes a huband at least one sensor node. The hub is configured to be attached to asurface (e.g., the skin) of a user. The hub is further configured totransmit electrical power and/or data signals into the surface (andthrough the skin) and to receive power and/or data signals transmittedthrough skin to the surface. The at least one sensor node is configuredto be attached to the surface. The at least one sensor node is furtherconfigured to receive the electrical power and/or data signals from thehub through the surface and to transmit the response data signals intothe surface (and through the skin). The electrical power from the hubpowers the at least one sensor node and causes the at least one sensornode to generate sensor information that is transmitted back to the hubwithin the response data signals.

According to some embodiments, a method of synchronizing nodes within anon-body sensor network is disclosed. The method includes transmitting,by a master hub located on a surface (e.g., skin) of a user, aninitialization electrical current pulse into the surface. The methodfurther includes receiving, by at least one sensor node located on thesurface, the initialization electrical current pulse from the surface.The method further includes transmitting, by the at least one sensornode, an acknowledgment electrical current pulse into the surface aftera pre-determined delay and in response to receipt of the initializationelectrical current pulse. The method further includes detecting, by themaster hub, the acknowledgment electrical current pulse, andtransmitting, by the master hub, a triggering electrical current pulseinto the surface. The triggering electrical current pulse includingelectrical power and data. The method further includes receiving, by theat least one sensor node, the triggering electrical current pulse fromthe surface. The electrical power and data triggering the at least onesensor node to begin generating sensor information.

Additional aspects of the disclosure will be apparent to those ofordinary skill in the art in view of the detailed description of variousembodiments, which is made with reference to the drawings, a briefdescription of which is provided below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood from the following descriptionof exemplary embodiments together with reference to the accompanyingdrawings, in which:

FIG. 1 is a schematic diagram of an on-body, multi-sensor system, inaccord with aspects of the present disclosure;

FIG. 2 is a schematic diagram of a master hub and sensor nodes of theon-body, multi-sensor system of FIG. 1, in accord with aspects of thepresent disclosure;

FIG. 3 is a detailed schematic diagram of an electrical power and datatransceiver of a sensor node, in accord with aspects of the presentdisclosure;

FIG. 4 is a timing diagram of electrical power and data transmissionwithin the on-body, multi-sensor system of FIG. 1, in accord withaspects of the present disclosure;

FIG. 5A is a bottom view of a schematic diagram of an exemplary sensornode, in accord with aspects of the present disclosure;

FIG. 5B is a top view of a schematic diagram of the exemplary sensornode of FIG. 5A, in accord with aspects of the present disclosure;

FIG. 6A is a diagram of an integrated master hub placed on the body of auser, in accord with accord with aspects of the present disclosure;

FIG. 6B is a diagram of contacts of the master hub of FIG. 6A inrelation to the body of the user, in accord with aspects of the presentdisclosure; and

FIG. 6C is a diagram of a gap between the master hub and the body inFIG. 6A, in accord with aspects of the present disclosure.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Although the present disclosure contains certain exemplary embodiments,it will be understood that the disclosure is not limited to thoseparticular embodiments. On the contrary, the present disclosure isintended to cover all alternatives, modifications, and equivalentarrangements as may be included within the spirit and scope of thedisclosure as further defined by the appended claims.

The present disclosure is directed to an on-body, multi-sensor network.Within the network is a node, also referred to herein as a master nodeor master hub. The master hub provides the electrical power and/or datato the remaining nodes within the network, also referred to herein assensor nodes or sensor patches. Both the master hub and the sensor nodescan be located on a body, such as a user's body (e.g., human or animalbody). The sensor nodes can be distributed across the body and remotefrom (e.g., not physically connected to) the master hub.

The form factor of both the master hub and the sensor nodes can allowfor the master hub and the sensor nodes to be placed on a regular or anirregular surface of an object (e.g., the body of the user, such as onthe skin of the user). For example, the master hub and the sensor nodecan be provided with one or more adhesive surfaces (e.g., pressuresensitive adhesives, permanent adhesives, and/or removable adhesiveelements such as adhesive tapes) in order to attach the master hub andthe sensor node to the surface of the body of the user. In accordancewith some embodiments, the master hub and/or one or more sensor nodescan be coupled (e.g., via adhesive, stitching, or hook and loopfasteners) to clothing, a bandage, or a brace that can be worn on thebody and configured to position the master hub and/or one or more sensornodes in contact with the surface of the body of the user. In accordancewith some embodiments, the master hub and/or one or more sensor nodescan be held in place on the surface of the body by adhesive tape or atight fitting garment, bandage or brace.

When coupled to the surface of an object, the master hub can supplyelectrical power and/or data to the sensor node through the surface ofthe object, such as through the skin of the body of a user. The sensornode acquires sensor information pertaining to the object, such as thebody of the user, and operates based on the electrical power transmittedby the master hub through the object to the sensor node. Thus, thenetwork operates based on the transmission of electrical power and/ordata between nodes using a user's body (e.g., a human or animal body) asthe transmission medium. More specifically, the network uses the skin ofthe user's body as the transmission medium for electrical power and/ordata transmission. Biological tissues have noticeable reactance from 5kHz to 1 MHz. The peak reactance is at 50 kHz. Bioimpedance ofsignificant physiological interest lies between 10 kHz to 100 kHz.Beyond 100 kHz, the reactance drops rapidly allowing higher electricalcurrent to be injected into the body safely. Alternatively, thereactance drop allows more reliable transmission of electrical signalsthrough the body at lower currents. However, radio channels exist above300 kHz. These radio channels can interfere with signal of interest.Therefore, the frequency band from 100 kHz to 300 kHz can be used forintra-body signal transmission with the least interferences. However,other frequency bands can be used for intra-body signal transmissiondepending on the application and transceiver technologies (e.g., spreadspectrum and QAM) used. Other frequency bands that can be used forintra-body signal transmission include, for example, bands in the 5 KHzto 10 MHz range, the 2 MHz to 30 MHz range including the 3 MHz to 7 MHzrange, and the 13 MHz to 20 MHz range.

According to some configurations of the present disclosure, the sensornodes do not require separate on-board electrical power sources.Instead, the sensor nodes receive electrical power from the master hubtransmitted across the skin of the user's body. In addition, signals andcan be carried within the electrical power signals, allowing the masterhub to both power and communicate with the sensor nodes.

Transmitting the electrical power and the data signals through theuser's body alleviates the physical burdens imposed on sensor systems,such as each sensor node requiring a discrete, on-board power source(and signal wires to the hub), and facilitates a more streamlined andcomfortable design. Moreover, with the master hub as the power source,the sensor nodes can be smaller and/or provide for greater functionality(e.g., additional sensors) and persistence by not requiring repeatedremoval from the user's body for recharging. By transmitting electricalpower and/or data through the skin of the user's body, rather than overthe air, the network can utilize lower power compared to comparablewireless methods, while also providing a higher level of security by notbeing susceptible to interception of over the air transmissions.

Turning now to the drawings, FIG. 1 shows an on-body, multi-sensorsystem 100, in accord with aspects of the present disclosure. The system100 includes a master hub 102 and a plurality of sensor nodes 104 a-104n (collectively referred to as sensor nodes 104). However, althoughillustrated and described as a multi-sensor system 100, the presentinvention includes the system 100 having only two nodes (e.g., themaster hub 102 and one sensor node 104).

The master hub 102 provides electrical power and/or data to the sensornodes 104 located across a body 106 of a user. More specifically, themaster hub 102 transmits the electrical power and data to the sensornodes 104 across the skin 106 a of the body 106. In response toelectrical power and data from the master hub 102, the sensor nodes 104transmit data (e.g., response data) back to the master hub 102 acrossthe skin 106 a. The response data can include sensor information fromone or more sensors of the sensor nodes 104, which is generated and/orcollected based on the sensor nodes 104 receiving the electrical powerfrom the master hub 102. Sensor information includes, for example,motion information (e.g., acceleration), temperature (e.g., ambient andof the sensor), electrical signals associated with cardiac activity,electrical signals associated with muscle activity, changes inelectrical potential and impedance associated with changes to the skin,biopotential monitoring (e.g., electrocardiography (ECG),electromyography (EMG), and electroencephalogram (EEG)), bioimpedancemonitoring (e.g., body-mass index, stress characterization, and sweatquantification), galvanic skin response information, and opticallymodulated sensing (e.g., photoplethysmography and pulse-wave velocity).The response data can also include status information about the statusof the sensor node 104 including, for example, the configuration of thenode (e.g., sensor operating parameters such as frequency or mode ofoperation). Thus, the master hub 102 supplies the sensor nodes 104 withelectrical power rather than, for example, the sensor nodes 104including on-board discrete power sources, such as chemical energysources (e.g., batteries).

In some aspects, the master hub 102 is a standalone, dedicated masterhub. In other aspects, the master hub 102 can be embodied in a device,an object, and/or an item. By way of example, and without limitation,the master hub 102 can be embodied in a device that is worn by the user,such as a fitness tracker, a smart watch, a wristband, jewelry (e.g.,rings, earrings, bracelets, etc.), an article of clothing (e.g., shirts,gloves, hats, socks, pants, etc.) or protective gear (e.g., helmet orbody or limb padding), etc., which contacts or is close to the skin 106a of the user. Further, although the user of FIG. 1 is illustrated as ahuman, the user can be any biological entity with skin that permits thetransmission of electrical power and/or data.

The location of the master hub 102 on the body 106 can vary. In someaspects, the master hub 102 is centrally located on the body 106 so thatthe outlying sensor nodes 104 all are approximately the same distancefrom the master hub 102. Exemplary locations for a centrally locatedmaster hub 102 include the chest, the back, the abdomen, the uppertorso, and the like. By way of example, and without limitation, a masterhub 102 centrally located on the body 106 can be embodied in an articleof clothing. Alternatively, the master hub 102 may not be centrallylocated. Instead, the master hub 102 can be located on an extremity ofthe body 106, such as at the wrist, the ankle, the head, and the like.By way of example, and without limitation, a master hub 102 locatedaround the wrist of the body 106 can be embodied in a smart watch. Themaster hub 102 can also be embedded (e.g., hidden) in other body wornelements, such as belts, shoes, hats, gloves, braces (e.g., wrist,ankle, knee, chest, neck braces). The master hub 102 can also beincorporated into devices that come in contact with a portion of thebody, such as a seat, a handle (e.g., exercise bike, treadmill,elliptical machine, dumbbell, exercise bar), or standing platform orfootrest.

In some aspects, the system 100 further includes a computer device 108.The computer device 108 can be any smart device, such as a smartphone, atablet, a laptop, a desktop, etc., that is capable of communicating withthe master hub 102. Data, such as sensor information, generated by thesensor nodes 104 can be transmitted back to the master hub 102 asresponse data. From the master hub 102, the response data can betransmitted to the computer device 108 for additional processing,analysis, storage, and/or transmission to additional devices or systems(e.g., the cloud, devices or systems remote from the system 100).Alternatively, the response data can be processed by the master hub 102and processed response data can transmitted to the computer device 108for additional processing, analysis, storage, and/or transmission to thecloud, additional devices or systems. Communications between the masterhub 102 and the computer device 108 can be wired or wireless.Preferably, communications between the master hub 102 and the computerdevice 108 are based on wireless communication protocols such as, forexample, Wi-Fi, Bluetooth, Bluetooth Low Energy, Zigbee, and the like.However, the wireless communications can be based on other protocols,including proprietary protocols, without departing from the concepts ofthe present disclosure.

Based on the master hub 102 transmitting the electrical power to thesensor nodes 104, the sensor nodes 104 do not require an internal oron-board power source. Accordingly, the sensor nodes 104 can fit on thebody 106 in various locations without being constrained by the size,weight, and/or inflexibility of an on-board power source. In doing so,the system 100 facilitates the operation and placement of the sensornodes 104. Further, the sensor nodes 104 can be optimized for theparticular sensing modality of interest, which improves the sensor nodes104 by allowing for better signal quality, better data collection, andthe like. The electrical power and data transmitted from the master hub102 to the sensor nodes 104 can be further tailored for each specificsensing modality, such as transmitting data in the form of specificalgorithms for each sensor node 104 to execute.

In accordance with some embodiments, the sensor nodes 104 can include anonboard power storage component such as a battery or a capacitorconfigured to store power received from the master hub 102. In thisconfiguration, the power received from by the sensor node 104 from themaster hub 102 can be stored to allow the master hub 102 to be chargedor replaced and to accommodate short duration power disruptions. Thesize of the power storage component can be determined based on theoperating parameters of the sensor node 104, such as its operating powerload.

In some aspects, the sensor node 104 is a standalone device. In otheraspects, the sensor node 104 can be embodied in other devices, objects,and/or items that come into contact with the body 106. By way ofexample, and without limitation, the sensor node 104 can be embodied ina device, object, and/or item that is worn by the user, such as awristband, jewelry (e.g., rings, earrings, bracelets, etc.), an articleof clothing (e.g., shirts, gloves, hats, socks, pants, etc.) skin 106 aof the user. By way of additional examples, the sensor node 104 can beembodied in furniture (e.g., chair, stool, bed, couch, etc.). In someaspects, the sensor node 104 can be embodied in objects found in amedical setting, such as a doctor's office, a hospital, and the like.Such specific examples include an examination chair, a hospital bed, andthe like. Further, although the user of FIG. 1 is illustrated as ahuman, the user can be any biological entity with skin that permits thetransmission of electrical power and/or data.

With the skin-based transmission of electrical power and/or data, themaster hub 102 can estimate the locations of the sensor nodes 104 on thebody 106 via the time required for communication signals to betransmitted and received from each sensor node 104, also referred to astime-of-flight. The time-of-flight can be used to approximate thedistance between the master hub 102 and each sensor node 104.Time-of-flight can be measured using various methods. According to onemethod, the master hub 102 (or a sensor node 104) can emit a knownsignal, such as a brief pulse. In some aspects, the signal or briefpulse can include known content, such as known broadband frequencycontent. As the signal or brief pulse propagates across the body 106,the rate of change of phase with frequency increases. By measuring thechange in the signal, and comparing the change to the original signal,the master hub 102 (or sensor node 104) can determine the travel time.Because the propagation speed of electrical signals through tissue isknown, the travel time can be related to the travel distance, such asthe travel distance between the master hub 102 and a sensor node 104, orbetween two sensor nodes 104. Thus, based on the travel time, the masterhub 102 (or sensor node 104) can determine the distance between it andanother sensor node 104. The determination of location can be based on around trip (i.e., from the master hub 102, to the sensor node 104, andback to the master hub 102), or based on a one-way trip (i.e., from themaster hub 102 and to the sensor node 104). In the case of a one-waytrip, the sensor node 104 can be pre-programmed with information (e.g.,known signal, frequency, etc.) of the on the brief pulse sent by themaster hub 102 to determine the travel time.

If the master hub 102 knows its location on the body 106, based on theapproximate distances between the master hub 102 and the sensor nodes104, the master hub 102 can determine where the sensor nodes 104 arelocated on the body 106. With the known locations, the master hub 102can vary one or both of the electrical power and data transmitted to thesensor nodes 104 based on a correspondence between the location of thesensor nodes 104 and, for example, the functionality and/or sensormodality associated with the location. In some aspects, thedetermination of the sensor node locations based on the approximatedistance is sufficient for determining when and/or how to alter theelectrical power and/or data sent to the sensor node 104. However,time-of-flight determination of the sensor node locations can becombined with additional location determination methodologies, such aslocation detection algorithms executed by the sensor nodes 104, toprovide a more accurate estimation of the locations of the sensor nodes104.

In some aspects, the sensor nodes 104 can be configured to determine thelocations of the other sensor nodes 104. The master hub 102 can transmitelectrical power and data to the sensor nodes 104 that cause the sensornodes 104 to transmit location-related data. The other sensor nodes 104can then receive the location-related data and respond back to thesensor nodes 104. This communication arrangement allows the sensor nodes104 to determine the locations of the other sensor nodes 104 throughtravel times of the data.

Referring to FIG. 2, FIG. 2 shows a schematic view of the master hub 102and the sensor nodes 104 of FIG. 1, in accord with aspects of thepresent disclosure. Referring first to the master hub 102, the masterhub 102 includes, for example, a power source 200, memory 202, a powertransmitter and data transceiver 204 for communicating with the sensornodes 104, a communications interface 206 for communicating with thecomputer device 108, and a processor 208.

The power source 200 provides the electrical power within the master hub102 and to the sensor nodes 104 within the system 100. To any extent themaster hub 102 may be constrained by the inclusion of an on-board powersource 200, the location of the master hub 102 on the body 106 can beindependent of a specific location. For example, whereas a sensor node104 should be located in a location related to the sensor modality, themaster hub 102 can be remote from the location without impacting thesensing. Thus, the placement of the master hub 102 within the system 100is not negatively impacted by the inclusion of the power source 200.Further, the power source 200 can include various conventional powersources, such as a super-capacitor or one or more rechargeable ornon-rechargeable batteries or cells having various battery chemistries,such as lithium ion (Li-ion), nickel-cadmium (NiCd), nickel-zinc (NiZn),nickel-metal hydride (NiMH), zinc and manganese(IV) oxide (Zn/MnO₂)chemistries, to name a few examples. In some aspects, the power source200 can be an electrical wall outlet that the master hub 102 directlyconnects to, or connects to through, for example, a power adapter (e.g.,alternating current adapter). In some aspects, the power source 200 canbe a component that harvests non-electrical energy, such as thermalenergy, kinematic energy, and/or radio-frequency energy, and convertsthe energy into electrical energy. However, the power source 200 can bevarious other power sources not specifically disclosed herein.

The memory 202 stores various instructions and algorithms for both thefunctioning of the master hub 102 and the sensor nodes 104. The memory202 can be any type of conventional memory, such as read only memory(ROM), read-write memory (RWM), static and/or dynamic RAM, flash memory,and the like. In some aspects, data received from the computer device108 can be written to the memory 202 for updating the instructions andalgorithms stored on the master hub 102, such as for updatinginstructions and algorithms based on newly developed sensor nodes 104.And data from the memory 202 can be written to memory of the sensor node104 to reconfigure them and, for example, update the firmware or otheroperating instructions of the sensor node 104.

The power transmitter and data transceiver 204 can be configured totransmit electrical power and data to the sensor nodes 104. The powertransmitter and data transceiver 204 is configured to modulate theelectrical power with the data, or data signals (e.g., analog signals),to transmit the data on the carrier of the electrical power. Thus,electrical power and data can then be received by the sensor nodes 104and demodulated and/or rectified to cause the sensor nodes 104 tooperate. More specifically, the power transmitter and data transceiver204 generates a time-varying electromagnetic wave that propagatesthrough the body 106 and is eventually received and rectified by sensornodes 104. The power transmitter and data transceiver 204 can include atransceiver circuit comprised of an amplifier whose output drives anelectrode coupled to the skin 106 a. The transceiver circuit can includecomponents such as, but not limited to, crystals, LC-tank oscillators,microelectromechanical system (MEMs) oscillators, processorgeneral-purpose input/output (GPIO) ports, frequency synthesizers, andring-oscillators to generate the output. The power output can becontrolled by modifying the gain of the amplifier in real time. Anadjustable impedance matching network may be included so that themaximum power is transmitted through the surface medium (e.g., skin 106a) to ensure the electromagnetic wave optimally propagates. Theadjustable impedance matching network may include various capacitors,inductors, and resistors using various techniques such as, but notlimited to, pi-matching, t-matching, and distributed matching networks.

The communications interface 206 can be any traditional communicationsinterface for communicating with the computer device 108, such as onebased on the wireless communication protocols of Wi-Fi, medicaltelemetry, Bluetooth, Bluetooth Low Energy, Zigbee, and the like, forexample, based on open 2.4 gigahertz (GHz) and/or 5 GHz onradiofrequencies, and the like. However, as described above, thecommunications interface 206 can also support wired communications withthe computer device 108.

The processor 208 controls the operation of the master hub 102. Theprocessor 208 can be various types of processors, includingmicroprocessors, microcontrollers (MCUs), etc., that are capable ofexecuting programs and algorithms, and performing data processing.Specifically, the processor 208 executes one or more instructions and/oralgorithms stored in the memory 202 or transmitted from the computerdevice 108, which cause the master hub 102 to transmit electrical powerand data to the sensor nodes 104, receive response data from the sensornodes 104, and aggregate, process, analyze, and/or store the responsedata. In some aspects, the processor 208 analyzes and/or processes theresponse data from the sensor nodes 104, such as the sensor information,prior to transmitting the response data to the computer device 108. Inaddition or in the alternative, the processor 208 can simply cause themaster hub 102 to transmit the response data to the computer device 108,such as when the computer device 108 is actively communicating with themaster hub 102.

Referring to the sensor nodes 104 of FIG. 2, the sensor nodes 104 can belocation specific sensory platforms that are placed at specificlocations on the body 106 for location-specific sensing. The sensornodes 104 receive the transmitted electrical power and data from themaster hub 102 to execute sensing, algorithms, and communicate back tothe master hub 102. Further, because the sensor nodes 104 receive theelectrical power from the master hub 102 required for operation, thesensor nodes 104 do not include discrete power sources for the overalloperation of the sensor nodes 104 except that the sensor node caninclude power storage components, such as capacitors and even smallbatteries to provide power in the event of a temporary powerdisruption).

In some aspects, the sensor node 104 can stream sensor information backto the master hub 102. Such a sensor node 104 can be considered a simplenode. Alternatively, the sensor node 104 can store the sensorinformation on the sensor node 104 prior to transmitting the sensorinformation to the master hub 102. Still further, the sensor node 104can alternatively process the sensor information prior to transmittingthe sensor information to the master hub 102. Processing of the sensorinformation can include, for example, smoothing the data, analyzing thedata, compressing the data, filtering the data, and the like. Such asensor node 104 can be considered a smart node. Thus, the functionalityof the sensor node 104 can vary.

The configuration of the sensor nodes 104 can vary depending on thespecific modality and/or functionality of the sensor(s). However, ingeneral, the sensor nodes 104 include a processor 210, one or moresensors 212, and an electrical power receiver and data transceiver 214.

The processor 210 performs the digital signal processing and dataanalysis of the sensor information generated and/or collected by the oneor more sensors 212. In some aspects, the data analyses of the sensorinformation includes, for example, executing one or more processes forsmoothing the data, analyzing the data, compressing the data, filteringthe data, and the like. In some aspects, the processing includesexecuting one or more stored or transmitted (e.g., from the master hub102) pattern recognition algorithms to detect one or more pre-definedpatterns in the data. However, in some instances, the data or sensorinformation (e.g., raw data) can be streamed back to the master hub 102without being processed. Instead, for example, the processing and/oranalyzing of the data or sensor information can instead be solelyperformed at the master hub 102 or the computer device 108. Theprocessor 210 can be various types of processors, includingmicroprocessors, MCUs, etc., that are capable of executing algorithmsand data processing, particularly based on the lower electrical powerlevels transmitted from the master hub 102. In some aspects, theprocessor 210 can include memory for storing one or more algorithmsperformed by the sensor nodes 104, and for storing informationtransmitted from the master hub 102. Alternatively or in addition, thesensor nodes 104 may include memory that is independent from theprocessor 210. In some embodiments, the sensor nodes 104 are slave nodesor dumb nodes and function based only on the data communication from themaster hub 102 and do not include instructions, algorithms, or otherdata required for functioning. Alternatively, the sensor nodes 104 canbe smart nodes that receive electrical power and triggering signalsand/or instructions (e.g., data) from the master hub 102, but includethe necessary instructions, algorithms, or data internally forgenerating and/or collecting sensor data and transmitting sensor dataand other information back to the master hub 102. By way of example, andwithout limitation, the processor 210 can be a Cortex-M Series MCU byARM® Ltd., an MSP430 MCU by Texas Instruments Inc., and the like.

The one or more sensors 212 perform the sensing functionality on thesensor nodes 104. The sensors 212 can be various types of sensors havingvarious types of sensing modalities. According to some embodiments, thesensors 212 include heat flux sensors, accelerometers or gyroscopes(e.g., motions sensors), electrocardiogram (ECG or EKG) sensors,pressure sensors, heart rate monitors, galvanic skin response sensors,sweat sensors, non-invasive blood pressure and blood oxygen saturationmonitors, pedometers, optical sensors, acoustic sensors, blood glucosesensors, and the like. However, the sensor nodes 104 can includeadditional sensors not explicitly disclosed herein without departingfrom the spirit and scope of the present disclosure. By way of somespecific examples, the one or more sensors 212 can include an ADS1191biopotential sensor by Texas Instruments, Inc., an ADXL362 accelerometerby Analog Devices, and the like.

In some aspects, one or more components of the sensor nodes 104independent of the sensors 212 can be considered a sensor. For example,components of the sensor nodes 104 configured to receive electricalpower and transmit and receive data can also be configured for sensing.Specifically, electrical contacts used for receiving the electricalpower can be configured to function as galvanic skin sensors, ECG or EKGsensors, and the like. Accordingly, in some aspects, a sensor node 104may not include a sensor 212, per se, where the components of the sensornode 104 themselves are capable of sensing characteristics and/orproperties of the skin 106 a and/or the body 106.

The electrical power receiver and data transceiver 214 allows the sensornodes 104 to receive electrical power from the master hub 102, and toreceive data from and transmit data to the master hub 102, as well asfrom and to the other sensor nodes 104 within the system 100. Thetransceiver 214 extracts the data and the electrical power from thereceived signals to both power the sensor node 104 and provide the datafor executing algorithms and processing data generated by the sensors212. The data can include instructions and/or commands to the sensornodes as well as firmware updates and other programs or algorithms to beexecuted by the sensor node. The transceiver 214 functions based on theproperties of the skin 106 a of the body 106 as described above withrespect to the power transmitter and data transceiver 204.

FIG. 3 shows a detailed schematic of the transceiver 214, in combinationwith the processor 210, in accord with aspects of the presentdisclosure. Although described with respect to the transceiver 214, asmentioned above, the power transmitter and data transceiver 204 of themaster hub 102 can include similar components as the transceiver 214 fortransmitting and receiving electrical power and data transmission. Insome aspects, the transceiver 214 includes one or more electricalcontacts 300, a biasing circuit 302, an amplifier 304, a demodulator306, an analog-to-digital converter 308, an alternating current drivecircuitry 310, and a power circuitry 312.

The electrical contacts 300 are formed of conductive material (e.g.,copper, silver, gold, aluminum, etc.) and provide the interface betweenthe sensor node 104 and the skin 106 a, or the sensor node 104 and theair gap between the sensor node 104 and the skin 106 a, for receivingelectrical power and transmitting and receiving data communication. Thesensor node 104 may include one or more electrical contacts 300. In someaspects, the sensor node 104 includes four contacts, with two contactsfor receiving and two contacts for transmitting. In some aspects, thecontacts 300 can be four contacts 300 configured as 4-wire measurementelectrodes.

For alternating electrical power transmitted into the skin, at around300 kHz or higher, the alternating electrical power can be detectednon-contact to the signal for as far as a few millimeters from the skin.Hence, the electrical contacts can be operated without being in contactwith the skin. Thus, in terms of the master hub 102 discussed above, aswell as the sensor nodes 104, the electrical contacts 300 do not needintimate coupling to the skin. However, in some aspects, a master hub102 configured with electrical contacts that do not contact the skin isequipped with a higher power transmitter. Without the requirement fordirect skin contact, the master hub 102 can be embodied in, for example,a smart watch, a fitness tracker, or other device powered by a powersource that is loosely secured to the body 106, without always being indirect contact with the skin 106 a. Accordingly, both the master hub 102and the sensor nodes 104 can be skin mounted or non-contact mounted. Forskin-mounted nodes, the electrical contacts are resistively coupled tothe skin. For non-contact mounted nodes, the electrical contacts arecapacitively coupled to the skin with a skin to electrode distance ofless than a few millimeters, such as less than or equal to about 3 mm.

As represented by the adjoining arrow, the contacts 300 can beelectrically connected to and in communication with a biasing circuit302, such as an analog front-end biasing circuit. The biasing circuit302 biases the data communication signal from the master hub 102, orother sensor nodes 104, for further processing by the components of thesensor node 104. The other components that perform the processinginclude, for example, the amplifier 304, which amplifies the data signalreceived from the master hub 102, or other sensor nodes 104. Asrepresented by the adjoining arrow, the amplifier 304 can beelectrically connected to and in communication with the biasing circuit302. The other components also include the demodulator 306, whichdemodulates the electrical power and data signal from the master hub 102to separate the data from the electrical power. As represented by theadjoining arrow, the demodulator 306 can be electrically connected toand in communication with the amplifier 304 for demodulating theamplified data. In combination with the analog-to-digital converter 308,the demodulator 306 digitizes the extracted data and forwards thedigitized data to the processor 210. As represented by the adjoiningarrows, the demodulator 306 can be directly electrically connected toand in communication with both the analog-to-digital converter 308 andto the processor 210. As represented by the 2-way arrow, the processor210 transmits information back to the demodulator 306 for transmissionto the master hub 102. By way of example, and without limitation, thedemodulator 306 can be a synchronous demodulator and configurable analogfilter, such as the ADA2200 made by Analog Devices, Inc. Further,although described herein as a demodulator, in some aspects, thedemodulator 306 can instead be a modem.

As represented by the adjoining arrow, the demodulator 306 can beelectrically connected to and in communication with alternating currentdrive circuitry 310. The alternating current drive circuitry 310generates alternating current pulses, or response data, forcommunicating with the master hub 102 and, potentially, with the othersensor nodes 104 within the system 100. The alternating current drivecircuitry 310 is controlled by the processor 210 to generate thealternating current pulses for responding to the master hub 102, andpotentially the other sensor nodes 104 within the system 100.

The power circuitry 312 controls the electrical power at the sensor node104 for executing algorithms and data processing based on the electricalpower from the master hub 102. In some embodiments, the power circuitry312 includes a capacitor or similar type of temporary power storagecomponent that stores power received from the master hub 102 duringexecution of the algorithms and processing of the data or sensorinformation. However, the power stored in the capacitor or similar typeof temporary power storage component is received from the master hub102, rather than being originally in the power source itself, such as ina chemical energy power source (e.g., battery).

Although electrical power and data transmission signals can betransmitted through the skin 106 a, noise may be introduced intosignals. In part because of the noise, time stamping of the signalspresents some issues. Accordingly, the above described circuitry of themaster hub 102 and the sensor nodes 104 include circuitry to remove thenoise and recover the underling signals. In some aspects, the circuitryis a phase lock loop (PLL). Moreover, most physiological sensorsgenerate data less than a few hundred bytes a second. Data communicationat about 300 to about 1200 baud is enough for transmitting real timedata for the sensors and the corresponding sensor nodes 104. A noiserejecting circuit based on a PLL with a carrier frequency between about100 kHz and about 300 kHz, and a bandwidth of about 30 kHz, can transmitdata communication at 1200 baud with simple communication scheme.Moreover, such a noise rejecting circuit can also detect the electricalcurrent pulses described above, as well as measure bioimpedance. Basedon this arrangement, as many as about 66 channels, one for each sensornode 104, can be allocated.

Although not shown, in some aspects, the sensor nodes 104 can includewired interfaces for connecting to one or more external sensors or othernodes within the system 100. The wired interfaces can be various typesof interfaces, particularly for connecting to components that use lowpower, such as an I²C interface and the like. Further, in some aspects,the sensor nodes 104 include components that provide for near-fieldcommunication (NFC) capability, or other similar low-power, wirelesscommunication protocols, for episodic sampling upon interrogation by areader. For example, in addition to one or more electrical contacts forreceiving the electrical power and data from the master hub 102, thesensor nodes 104 can include a wire coil for interrogation by aNFC-capable smart device (e.g., smartphone, tablet, and the like).

Referring to FIG. 4, FIG. 4 is a timing diagram of electrical power anddata transmission within the on-body, multi-sensor system 100 of FIG. 1,including data synchronization, in accord with aspects of the presentdisclosure. The transmission of the electrical power and data relies onan electrical current being able to travel across the skin 106 a of thebody 106, similar to an electrical current traveling through water.Indeed, the propagation velocity of the electrical current across theskin 106 a is approximately one-tenth of the speed of light. Further,the longest conductive path between any two points on the body 106 isabout 2 meters. Therefore, the signal propagation delay of an electricalsignal from one point to another point across the body 106 is about 70nanoseconds (ns). This delay is below the synchronization requirement ofa majority of the physiological sensors for proper interpretation of thesignals.

For synchronization, the master hub 102 first transmits an electricalcurrent pulse 400 a into the skin 106 a of the body 106. The electricalcurrent pulse 400 a is of a fixed duration and amplitude, or amplitudepattern, and at a dedicated frequency channel for initialsynchronization. According to some aspects, the master hub 102continuously, periodically, semi-periodically, or on-demand transmitsthe electrical current pulse 400 a so that sensor nodes 104 newly placedon the body 106 can be synchronized within the system 100.

The sensor nodes 104 on the body 106 then detect the electrical currentpulse 400 a, as shown by the received electrical current pulses 402a-402 n (collectively received current pulses 402). The sensor nodes 104detect the electrical current pulse 400 a with less than about 1microsecond (μs) of a delay. The sensor nodes 104 then transmitacknowledge pulses 404 a-404 n (collectively acknowledge pulses 404)after a pre-determined delay and for the master hub 102 to detect, asindicated by the received current pulse 400 b. A synchronized signalacquisition can then be undertaken by the sensor nodes 104.Specifically, the master hub 102 transmits an electrical power and datapulse 400 c, which triggers the synchronized signal portions 406 a-406 n(collectively synchronized signal portions 406). The electrical currentpulse 400 c is of a fixed duration and amplitude, or amplitude pattern,and at a dedicated frequency channel for triggering, which is differentthan the initial frequency initialization channel. The timing andsynchronization scheme and system architecture to perform sensorsynchronization and measurement triggering disclosed above enablessensor nodes 104 to synchronize at time delays less than 1 μs and powerlevels of about 1.5 milliwatts (mW), which is lower than radio frequencywireless communication.

Referring to FIGS. 5A and 5B, an exemplary sensor node 500 is shown, inaccord with aspects of the present disclosure. By way of example, andwithout limitation, the sensor node 500 may be a conformal sensor nodeformed of a flexible substrate and circuit for conformal attachment tothe surface (e.g., skin 106 a) of a user. The sensor node 500 isconfigured to generate sensor information associated with the user uponwhich the sensor node 500 is attached.

FIG. 5A shows the bottom of the sensor node 500, and FIG. 5B shows thetop of the sensor node 500. As shown in FIG. 5A, the sensor node 500includes four contacts 502 (e.g., contacts 300). The contacts 502contact the skin 106 a of a user to receive and transmit signals, suchas the electrical power and/or data, from and into the skin. However, insome embodiments, a small air gap can be between the contacts 502 andthe skin 106 a, and the signals can be transmitted across the air gap,as described above.

In some aspects, two of the contacts 502 are electrically configuredand/or wired within the circuit of the sensor node 500 to receive theelectrical power and/or data, and the other two of the contacts 502 areelectrically configured and/or wired within the circuit of the sensornode 500 to transmit electrical power and/or data. However, in someaspects, all of the contacts 502 can be electrically configured and/orwired to both transmit and receive the electrical power and/or data.Further, although only four contacts 502 are shown, the number ofcontacts may vary. For example, the sensor node 500 may have one or morecontacts 502.

As described above, the contacts 502 may also be used by the sensor node500 to generate sensor information. For example, the sensor node 500 maybe a galvanic skin sensor. One or more of the contacts 502 may beelectrically configured and/or wired to generate sensor information withrespect to, for example, bioimpedance, in addition to receiving andtransmitting electrical power and/or data. Thus, in the case of sensornode 500, the sensors (e.g., sensors 212) are, in part, the contacts502.

The sensor node 500 further includes sets of vertical interconnectsaccesses (VIAs). Specifically shown in FIG. 5A are the bottoms 504 ofthe sets of VIAs. The VIAs transfer the electrical power and/or databetween layers of the circuits of the sensor node 500. For example, thebottoms 504 of the sets of VIAs are electrically connected to thecontacts 502 to transfer the electrical power and/or data from a bottomcircuit layer of the sensor node 500 to a top circuit layer of thesensor node 500.

Referring to FIG. 5B, FIG. 5B shows the tops 506 of the sets of VIAs.The tops 506 of the sets of VIAs are electrically connected to a topcircuit layer of the sensor node 500 for providing the electrical powerand/or data to the top circuit layer. With respect to the sensor node500, the sensor node 500 includes one or more components within the topcircuit layer for analyzing and/or processing the electrical powerand/or data signal received by the contacts 502. For example, althoughnot shown, the sensor node 500 can include the processor 210 and thetransceiver 214 above the tops 506s of the VIAs. The processor 210 andthe transceiver are electrically connected to the tops 506 of the VIAsso as to be electrically connected to the contacts 502. Based on theprocessor 210 and the transceiver 214 being electrically connected tothe contacts 502, the processor 210 rectifies the electrical power andthe transceiver demodulates the data received at the contacts 502. Theprocessor 210 can then process the sensor information to be transmittedback to a master hub (e.g., master hub 102) through the contacts 502 andthe skin 106 a of the body 106. In some aspects, the sensor node 500further includes a grounding line 508.

According to the configuration of the sensor node 500, the sensor node500 can be placed on various locations of the body 106. Further, becausethe sensor node 500 does not have an on-board power source, the sensornode 500 receives the electrical power for operation by receivingelectrical power transmitted from a master hub (e.g., master hub 102)located on the body 106 but remote (e.g., not directly connected) fromthe sensor node 500. The electrical power, along with the data from themaster hub 102, is received by one or more of the contacts 502 andelectrically powers the sensor node 500.

Referring to FIGS. 6A-6C, a master hub 600 is shown coupled to the body106 of a user, in accord with aspects of the present disclosure.Referring to FIG. 6A, the master hub 600 may be, for example, integratedinto a smart watch. Specifically, the master hub 600 may be integratedinto the wristband of the smart watch. However, the master hub 600 canbe integrated into any one of the devices discussed above. Based on themaster hub 600 being integrated into a smart watch, or the wrist band ofthe smart watch, the master hub 600 is attached to, for example, theskin 106 a around the wrist of the user's body 106.

Although not shown (for illustrative convenience), the master hub 600includes a power source (e.g., power source 200). The power sourcepowers both the master hub 600 and the smart watch, such as the timekeeping functionality and the communications functionality of the smartwatch with an off-body device (e.g., computer device 108), such as asmartphone that is communication with the smart watch, etc.

Referring to FIG. 6B, the master hub 600 includes contacts 602. Althoughfour contacts 602 are shown, the master hub 600 can have one or morecontacts. Similar to the contacts 502, the contacts are made of aconductive material (e.g., copper, silver, gold, aluminum, etc.).Through the contacts 602, the master hub 600 transmits and receiveselectrical power and/or data to and from the skin 106 a. The contacts602 may be in contact with the skin 106 a. Alternatively, the contacts602 may not be in contact with the skin 106 a. For example, depending onhow loose the wristband is, the contacts 602 may not always be incontact with the skin 106 a.

Referring to FIG. 6C, FIG. 6C shows a gap 604 that may be between thecontacts 602 (FIG. 6B) and the skin 106 a. Despite the gap 604, thehigher energy reserve of the smart watch allows the master hub 600 totransmit electrical power and/or data across the air gap 604, asdiscussed above. For example, as discussed above, at around 300 kHz orhigher, alternating current signals can be detected non-contact to theskin 106 a for as far as a few millimeters from the skin 106 a.Therefore, the master hub 600 can be operated non-contact while stillenabling electrical power and/or data transfer into the skin.

Although the foregoing disclosure is generally related to transmittingelectrical power and data transmission between the master hub 102 andthe sensor nodes 104, according to some aspects, only electrical poweror only data can be transmitted between the master hub 102 and thesensor nodes 104. For example, only electrical power can be transmittedby the master hub 102 to the sensor nodes 104 for smart sensor nodes 104that do not require transmitted data.

According to the above disclosure, the system 100 enjoys benefits overother multi-sensor systems on a user's body. For example, the system 100can be used in applications where multi-modal sensing is required, andwhere the specific modality of the sensing may vary across users or mayvary over time for the same user. For example, a user who wishes to gofor a run can use the system 100 to log heart rate, gait, posture, andsweat rate by using sensor nodes 104 optimized for each of these sensingmodalities. The master hub 102 can aggregate the data from each sensornode 104, fusing the data into insightful characteristics about theactivity the user is performing. Moreover, a user can quickly and easilychange the modalities of the system by changing the sensor nodes 104 onthe user's body. Further, the form factor of the sensor nodes 104 can besmaller, less obtrusive, and more conformal, while still enjoying thebenefits of, for example, continuous data generation by an on-body node(e.g., master hub 102) rather than, for example, periodic datageneration based on interrogation of the sensor nodes 104 by an off-bodycomputer device.

Other embodiments are within the scope and spirit of the invention. Forexample, due to the nature of software, functions described above can beimplemented using software, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations.

Further, while the description above refers to the invention, thedescription may include more than one invention.

What is claimed is:
 1. A method of synchronizing nodes within an on-bodysensor network, the method comprising: transmitting, by a master hublocated on a surface of a user, an initialization electrical currentpulse into the surface; receiving, by at least one sensor node locatedon the surface, the initialization electrical current pulse from thesurface; transmitting, by the at least one sensor node, an acknowledgeelectrical current pulse into the surface after a pre-determined delayand in response to receipt of the initialization electrical currentpulse; detecting, by the master hub, the acknowledge electrical currentpulse; transmitting, by the master hub, a triggering electrical currentpulse into the surface, the triggering electrical current pulseincluding electrical power and data; and receiving, by the at least onesensor node, the triggering electrical current pulse from the surface,the electrical power and data triggering the at least one sensor node tobegin generating sensor information.
 2. The method of claim 1, furthercomprising: transmitting, by the at least one sensor node, response dataincluding the sensor information into the surface; and receiving, by themaster hub, the response data from the surface.
 3. The method of claim2, further comprising: transmitting, by the master hub, the responsedata including the sensor information to a computer device located offof the user.
 4. The method of claim 1, wherein the initializationelectrical current pulse is of a fixed duration and a fixed amplitude,and at a dedicated initialization frequency.
 5. The method of claim 4,wherein the triggering electrical current pulse is of a fixed durationand a fixed amplitude, and at a dedicated triggering frequency,different than the dedicated initialization frequency.
 6. The method ofclaim 1, wherein the initialization electrical current pulse and thetriggering electrical current pulse are about 1.5 milliwatts.
 7. Themethod of claim 1, wherein the master hub transmits the initializationelectrical current pulse continuously, periodically, semi-periodically,or on-demand.